This aim of this research project is to elucidate the mechanism by which the small Tim (translocase of the inner membrane) proteins of the mitochondrial inner membrane space interact with each other and with their substrate proteins. The small, soluble Tim proteins (Tim8p, Tim9p, Tim10p, Tim12p, and Tim13p) share a conserved amino acid structure described as a "twin CX3C" motif, which has been identified as a possible site of disulfide bond formation. The presence and importance of disulfide bond formation to the structure and function of the small Tim proteins will be determined. Additionally, novel pathways in S. cerevisiae that are affected by the redox state of the cell will be identified. By varying the concentration of oxidizing and reducing agents, a screen of the S. cerevisiae deletion library can identify hypo- and hypersensitive redox mutants. The genes identified will be characterized biochemically and genetically to determine their role in cellular redox homeostasis. Also screened will be S. cerevisiae temperature sensitive mutants of the tim9, tim10, tim12, and tim22 alleles, all components of inner membrane translocation. Mitochondrial protein translocation is of enormous interest since the association of diseases to import dysfunction was established.